STAR – Precision Ball Screw Assemblies

Calculation Example
Service life
Operating conditions
The service life of the machine should be
40,000 operating hours with the ball
screw operating 60% of the time.
Calculation procedure
Average speed n m
Average load F m for variable load and
variable speed.
Required service life L
(revolutions)
The life L can be calculated by transposing
the formulas 7 und 8 errechnet werden:
Basic dynamic load rating C
Result and selection
The ball screw can now be selected from
the Dimension Tables:
RE 83 301/12.99 95
Proposed ball screw: 63 x 10
F1 = 50 000 N at n1 = 10 min-1 F2 = 25 000 N at n2 = 30 min
for q1 = 6 % of the duty cycle
-1 F3 = 8 000 N at n3 = 100 min
for q2 = 22 % of the duty cycle
-1 F4 = 2 000 N at n4 = 1 000 min
for q3 = 47 % of the duty cycle
-1 for q4 = 25 %
100 %
of the duty cycle
n m
6 + 22 47 25
100
10
100
30
100
100
100
1000
n m 304 min -1
F m
3 3 10 6
50000
304 100
F m 8757 N
L L h n m
L h
L h
C
Machine operating hours
40000
8757
3
60
60
100
L 24000 304 60
24000 h
437 760 000
10 6
25000 3 30 30
304 100
e.g. ball screw, size 63 x 10 R x 6-6, with
preloaded single nut with flange FEM-E-S,
basic dynamic load rating C = 88 800 N,
part no. 1512-6-4013.
5
1
3 100 47
8000
304 100
Machine operating hours
Ball screw operating hours
L 437 760 000 revolutions
C≈ 66492 N
Cross check
Service life of the selected ball screw in
revolutions L ≈ 1042 · 106 L
88 800
10 revolutions
6
8757
3
4
2000
25
3 1000
304 100
3
Life Lh in hours
L
1042 10
7
The life of the selected ball screw assembly
is thus greater than the required service
life of 24,000 hours (including operating
hours). A smaller ball screw could therefore
be selected.
6
h 304 60
Lh ≈ 57 167 hours